Actuators based on the piezoelectric principle are suitable for the highly accurate and very rapid control of actuating operations, such as are expedient, for example, for the activation of injection apparatuses or injection valves of internal combustion engines. In order to implement pronounced linear deflections of the piezoelectric actuators, these must consist of a multiplicity of individual piezoelectric elements stacked one on top of the other. The disadvantage of this is that the overall size assumes inadmissible dimensions for many applications. Thus, for example, the installation space for injection valves in the cylinder head of an internal combustion engine is limited in such a way that there is, as a rule, no room for piezoelectric actuators in the length dimension necessary for the desired actuating movements. For this reason, smaller piezoelectric actuators are used, the linear deflections of which are stepped up into larger deflections by suitable lever devices.
WO 99/17014 discloses, for example, an injection valve in which, for transmitting a deflection of a piezoelectric actuator to an actuating member and for stepping up this deflection, mechanical transmission elements are provided, which are essentially in the form of a cylinder, the boundary surfaces of which are of essentially triangular design, the corners being rounded. Sheetlike bearing regions are in this case formed as a result of the width of the transmission elements.
For example in conjunction with control valves for injection apparatuses, it is necessary for the actuator space to be sealed off with respect to other regions of the control valve. O-rings have already been used for this purpose. The use of O-rings presents problems, however, in as much as O-rings can be damaged relatively easily. This problem is aggregated further in that damage to an O-ring cannot readily be detected reliably during subsequent tests.
Compared with O-ring sealing off, a metallic sealing off of the actuator space therefore affords advantages, and, in preferred embodiments, there may be provision for the sealing surfaces to run perpendicularly with respect to the actuator axis. The surface pressure required for the sealing function may be applied, for example, via a connecting thread. In embodiments of this type with a metallic sealing off of the actuator space, however, there is the problem that the guide of the transmission element is not fastened nonpositively with respect to the actuator, but can move spatially within the play tolerance. This moveability may cause kinematic variations and therefore dispersions in the stroke step-up.